Peel and cut the potato into bite-sized pieces.

Rinse the potato briefly in water, place in a bowl, cover with plastic wrap, and microwave at 600W for 4 minutes.

Mash the potato while hot until smooth.

Mix the mashed potato with mayonnaise and a pinch of salt and pepper.

Cut the hanpen fish cakes in half horizontally.

Place a slice of cheese on one half of the hanpen, add the potato mixture, and sandwich with the other half. Cut in half again.

Wrap the hanpen sandwich in spring roll wrappers, sealing the edges with the cornstarch mixture.